Present methods for making peroxycarboxylic acids include mixing a carboxylic acid or anhydride with an oxidizing agent, such as hydrogen peroxide, in water and waiting. At ambient conditions, the reaction can take a week or more to reach desirable concentrations of peroxycarboxylic acid at equilibrium. In addition, regulations regarding and practices in shipping of ingredients such as hydrogen peroxide and acetic acid can limit the concentration, stability, content, or purity of these reagents and, therefore, of the resulting peroxycarboxylic acid. For example, acetic acid inevitably contains metal due to common shipping and handling practices. Conventional peroxycarboxylic acid compositions typically include short chain peroxycarboxylic acids or mixtures of short chain peroxycarboxylic acids and medium chain peroxycarboxylic acids (see, e.g., U.S. Pat. Nos. 5,200,189, 5,314,687, 5,409,713, 5,437,868, 5,489,434, 6,674,538, 6,010,729, 6,111,963, and 6,514,556).
Ongoing research efforts have strived for improved peroxycarboxylic acid compositions and methods of making them. In particular, these efforts have strived for methods that can more rapidly make purer and/or more stable peroxycarboxylic compositions even at a point of use.